Electron-tube arrangement for high-frequency communication



I Feb. 11, 1930. E. KlEHNE 7 1,746,430

ELECTRON TUBE ARRANGEMENT FOR HIGH FREQUENCY COMMUNICATION Filed March 12, 1925 N MWMMWNH :1 I i R g "5 g 11 2 g 7 3 6 INVENTOR ERICH KIEHNE TTORNEY Patented Feb. 11, 1930 UNITED STATES PATENT OFFICE,

- ERICH KIEHNE, 01E BERLIN, GERMANY, ASSIGNOR TO GESELLSCHAFT F'l 'R' DBAHT:

LOSE TELEGRAPHIE M. B, H., 01%. BERLIN, GERMANY, A CORPORATION OF GERMANY ELECTRON-TUBE. ARRANGEMENT FOR HIGH-FREQUENCY COMMUNICATION Applicatiomfiled March 12, 1925, Serial No. 14,868, and in Germany March 13, 1924.

My invention relates broadly to receivers for receiving high frequency signals such as are used in radio and, more particularly, toan arrangement employing a thermionic electron tube in which the tube circuits are regeneratively. coupled. a

An object of the invention is to provide such. an electron tube arrangement with means for indicating when the tube begins to generate oscillations and for stopping the generation of oscillations at their incipiency, thereby obviating harmful radiation with its consequent interference with neighboring receivers.

Other objects will be apparent from. the following specification and claims whenconsidered with the accompanying drawing in which Fig. 1 is a circuit embodying one form of my invention and Fig. 2: is. a modification.

In arrangements comprising electron tubes for the purposesof high frequency communi cation it hasbeengeneral practice, in order to realize as high an amplification aspossible, to use circuits utilizing regenerative coupling. If the adjustment of the regenerative coupling is made variable, and if the coupling is made too close,oscillations may be set up tending to disturb reception, andfurthermore, because of the fact that they may be radiated from the antenna, they are liable to disturb the reception of neighboring receivers. With the increasing number of stations for the reception of intelligence transmitted by means of high frequency waves, either by wireless or over long lines, the dis. turbances due to the radiation of energy at y these receiving stations become increasingly '40 harmful, so that it becomes absolutely imperative to provide means whereby the generation of such oscillations and the radiation of high frequency energy can be prevented.

The present invention is based upon the fact that there is a change'ofthe anode cur rent in a regeneratively coupled electron tube at the very incipiency of oscillations which maybe utilized in order to actuate a devlce whereby theosclllations 1n statu nascendi are suppressed in an automatlc manner. The fundamental idea underlying the invention, it will be noted, resides in the utilization of the change of theanode current during reception upon self-excitation being produced, for the actuation of a device which prevents the production of such oscillations. In the case of an electron tube which gives detector action by means of a grid leak and condenser this change of anode current I find to be a decrease.

My scheme can be carried into practice in various ways. In the particular type of receiving circuit shown in the disclosed embodiment, for instance, I find that it is practicable and satisfactory to employ a. relay which responds to the decrease of the anode current caused by self-excitation, and which causes a switching process by means of which the regenerative coupling is either discontinued, or loosened, or its effects lessened, so that no continued generation of oscillations will occur. A more strictly accurate statement' would, perhaps, be that the relay so alters the circuit that the oscillations are not sustained.

Fig. 1 illustrates the invention. as applied to a well knowntype of regenerativereceiver. Referring to that figure, 1 denotes an antenna having a parallel circuit consisting of an inductance 2 and a variable condenser 3 be tween it and the ground. The variable condenser 3 allows tuning of the antenna circuits to the desired wave length. The electron tube 4 is the usual three element type. The grid circuit is connected through a grid condenser 5 across condenser 3. The grid leak 6 is used to connect the grid to the filament in anyusual manner. When the relay8 is inthe position shown, the B-battery 14, the telephone 7, the winding of the relay 8, andthetickler coil 10 are all in the plate circuit. The tickler coil 10 is, of course, inductively coupled to the inductance 2 to give the desired feed-back intended. to amplify the reception. But there then. exists a plate circuit and a grid circuit which are inductively coupled, and when the mutual inductance is equal to or greater, up to certain extent, than the critical value to sustain oscillations the circuit willnot merely be regenerative but will become a generator of oscillations, which is an abnormal and undesirable condition.

The plate current flowing through the winding of relay 8 normally is sufficient to keep the relay contacts open. If the coupling between tickler coil 10 and inductance 2 is so tight that oscillations are generated, the relay 8 is deenergized because'of the drop in plate current caused by the tube 4 being set into incipient oscillation. The contacts of relay 8 then close and condenser 9' is placed in parallel with the relay winding and the tickler coil 10, thereby cutting down the feed-back appreciably, for the condenser 9 by-passes part of the high frequency current directly to the plate without it going through the inductance 10. This causes the incipient oscillations started in tube 4 to stop, which usually will cause the plate current to rise again. The increase in plate current then will cause the contacts of relay 8 to open and the shunt by-pass condenser 9 to be removed. 7

Unless the coupling between tickler coil 10 and inductance 2 is loosened, the tube probably will start to oscillate again. This cycle of events may continue indefinitely if some means is not taken to prevent its continuation.

Fig. 2 shows an arrangement like Fig. 1 but to which there has been added means to prevent continuous operation of the relay 8. When the current through relay 8 is weakened and contact is made the armature is held in its upper position by means of a permanent magnet n. (lo-operating with the armature and opposed to the attraction of the magnet 11. is the actuator p which is manually operable to break the contact of relay 8. hen actuator p is depressed, contact 11 in the antenna circuit also is broken. This is for the purpose of preventing radiation of newly restartedoscillations when the actuator 19, and consequently the armature of relay 8, are depressed, whether temporarily or permanently.

It will easily be seen that in the case of Fig. 1 the vibration of relay 8, and in the case of Fig. 2 the raised position of the relay armature, will serve to attract the attention of the operator to the fact that the feed-back coupling is too tight, and that the receiver is attempting to oscillate.

Having described my invention, I am entitled to all modifications and ramifications thereof as fall fairly within the spirit and scope of the following claims 1. In combination, means for receiving high frequency waves, an electron discharge device'coupled thereto and having its input and output circuits regeneratively coupled, automatic means adapted for permanently suppressing generation of oscillations at their incipient stage for so long as may be desired,

and nonautomatic means for restarting oscillations,

2. In combination, means for receiving high frequency waves, a thermionic tube having input and output circuits regeneratively coupled, said output circuit including means for feeding energy back into said input circuit, and means for automatically connecting a by-pass circuit in parallel with said feedback means only when oscillation begins in order to cut off the generation of oscillations at their incipiency.

3. An electron tube arrangement comprising a regeneratively coupled electron tube, and a magnetic device which responds to a change of the anode current upon oscillations being produced, to suppress the generation of oscillations.

4. An arrangement as specified in claim 3, wherein the device is a relay which lessens the regenerative coupling between the anode and grid circuits so that the oscillations will be caused to cease.

5. An arrangement as specified in claim 3, wherein the device is a relay which connects a shunt for the high frequency waves in parallel to part of the regeneratively coupled inductance.

6. An electron tube arrangement comprising a regeneratively coupled electron tube, a device which responds to a change of the anode current, upon oscillation being produced, to suppress the generation of oscillations. and means to retain said device in its position of response.

7. An arrangement as specified in claim 6, having means for restoring the device, after response, to its non-responsive condition, said means being so constructed that. jointly with the restoration of the device, the receiving circuit is opened.

8. In combination, an electron discharge device, grid and anode circuits arranged for regeneration, and means adapted to automatically prevent continued occurrence of oscillations permanently until reestablished nonautomatically.

9. In combination, an electron discharge device, grid and anode circuits arranged for regeneration, and automatic means adapted to prevent continued occurrence of oscillations at their beginning permanently and to indicate that oscillations are being prevented.

10. In combination, an electron discharge device, grid and anode circuits arranged for regeneration, automatic meansv adapted to prevent continued occurrence of oscillations at their beginning permanently, and nonautomatic means to restore the automatic means to initial condition when desired.

11. In combination, an antenna system, an electron discharge device, grid and anode circuits arranged for regeneration, automatic means adapted to prevent continued occurrence of oscillations at their beginning permanently, means to restore the automaticmeans to initial condition and means actuated by the restoring means for preventing radiation of the restarted oscillations from the antenna system.

12. In combination, an antenna system, an electron discharge device, grid and anode circuits arranged for regeneration, means to indicate when oscillations have begun, and means to restore the indicating means to normal condition and simultaneously to prevent radiation of oscillations from the antenna system.

ERIGH KIEHNE; 

